Few signaling molecules or extracellular matrix (ECM) genes have been identified as critical regulators of joint cartilage maintenance in the pathogenesis of osteoarthritis (OA) in mice or humans. Recently, we have identified the Notch signaling pathway as a novel and critical regulator of skeletal progenitor cell differentiation during early limb development, as well as, an integral mediator of chondrocyte proliferation and maturation during endochondral bone development. Here we present additional breakthrough discoveries identifying the Notch signaling effector, RBPjk, as a novel and critical regulator of normal articular cartilage and joint maintenance. Specifically, we have discovered that loss of RBPjk in nearly all cells of the joints (Prx1Cre; RBPjkf/f) results in 1) fibrosis and degenerationof the articular cartilage with a significant loss in ECM components, 2) meniscus fibrosis and degeneration, 3) subchondral bone sclerosis, 4) osteophyte formation, and 5) a progressive loss of the Prg4 (lubricin) expressing superficial articular cartilage. Based on these novel findings, w hypothesize that chondrocyte-specific RBPjk-dependent Notch signaling is required for articular cartilage and joint maintenance via regulation of ECM-related molecules, which ultimately controls PRG4 (LUBRICIN) expression, localization, and function within the articular cartilage. To test this hypothesis we have developed three specific aims geared at uncovering the cellular and molecular mechanisms by which RBPjk- dependent Notch signaling maintains articular cartilage. We will generate several mouse genetic models and in vitro articular chondrocyte culture or explant models to test whether: A) cartilage-specific RBPjk-dependent Notch signaling controls articular cartilage maintenance, B) RBPjk-dependent Notch signaling is required to maintain normal PRG4 expression, localization, and function, C) RBPjk and PRG4 genetically and functionally interact during articular cartilage maintenance, D) PRG4 overexpression can rescue the OA phenotype of Prx1Cre; RBPjkf/f mutant mice, E) RBPjk haploinsufficiency accelerates OA progression following traumatic joint injury, and F) transient Notch activation can suppress OA progression following traumatic joint injury. Data generated by this proposal wil likely identify the RBPjk-dependent Notch pathway as a potential target for developing disease modifying osteoarthritis drugs (DMOADs).

Public Health Relevance

We have identified the RBPJk-dependent Notch pathway as an important regulator of articular cartilage and joint maintenance. Our proposal will determine the exact Notch signaling mechanisms responsible for maintaining the articular cartilage phenotype and joint integrity. Data generated by this proposal wil likely implicate RBPjk-dependent Notch signaling in the regulation of specific cartilage-related extracellular matrix molecules, including TENASCIN-C and PRG4, and will likely identify the Notch pathway as a potential target for developing disease modifying osteoarthritis drugs (DMOADs).

Agency
National Institute of Health (NIH)
Institute
National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS)
Type
Research Project (R01)
Project #
5R01AR063071-05
Application #
9061598
Study Section
Skeletal Biology Development and Disease Study Section (SBDD)
Program Officer
Tyree, Bernadette
Project Start
2012-07-02
Project End
2017-05-31
Budget Start
2016-06-01
Budget End
2017-05-31
Support Year
5
Fiscal Year
2016
Total Cost
Indirect Cost
Name
Duke University
Department
Orthopedics
Type
Schools of Medicine
DUNS #
044387793
City
Durham
State
NC
Country
United States
Zip Code
27705
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Lawal, Rialnat A; Zhou, Xichao; Batey, Kaylind et al. (2017) The Notch Ligand Jagged1 Regulates the Osteoblastic Lineage by Maintaining the Osteoprogenitor Pool. J Bone Miner Res 32:1320-1331
Cao, Chike; Ren, Yinshi; Barnett, Adam S et al. (2017) Increased Ca2+ signaling through CaV1.2 promotes bone formation and prevents estrogen deficiency-induced bone loss. JCI Insight 2:
Shang, Xifu; Wang, Jinwu; Luo, Zhengliang et al. (2016) Notch signaling indirectly promotes chondrocyte hypertrophy via regulation of BMP signaling and cell cycle arrest. Sci Rep 6:25594
Rutkowski, Timothy P; Kohn, Anat; Sharma, Deepika et al. (2016) HES factors regulate specific aspects of chondrogenesis and chondrocyte hypertrophy during cartilage development. J Cell Sci 129:2145-55
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Wang, Cuicui; Inzana, Jason A; Mirando, Anthony J et al. (2016) NOTCH signaling in skeletal progenitors is critical for fracture repair. J Clin Invest 126:1471-81
Zhang, Yongchun; Sheu, Tzong-jen; Hoak, Donna et al. (2016) CCN1 Regulates Chondrocyte Maturation and Cartilage Development. J Bone Miner Res 31:549-59
Hamada, Daisuke; Maynard, Robert; Schott, Eric et al. (2016) Suppressive Effects of Insulin on Tumor Necrosis Factor-Dependent Early Osteoarthritic Changes Associated With Obesity and Type 2 Diabetes Mellitus. Arthritis Rheumatol 68:1392-402
Zhang, Hengwei; Sun, Wen; Li, Xing et al. (2016) Use of Hes1-GFP reporter mice to assess activity of the Hes1 promoter in bone cells under chronic inflammation. Bone 90:80-9

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